@article{ung-mou-93-prot,
  author = {Ron Unger and John Moult},
  title = {Finding the Lowest Free Energy Conformation of a Protein is an {NP}-Hard Problem: {Proof} and Implications},
  journal = {Bulletin of Mathematical Biology},
  volume = {55},
  number = {6},
  pages = {1183--1198},
  year = 1993
}